A gasket (also referred to as a head gasket) is disposed between a cylinder block (also referred to as an engine block) and a cylinder head in an internal combustion engine. The gasket is provided to seal around the cylinders, oil passage openings and coolant passage openings. Coolant flow around a water jacket is used to cool the engine block and other components including the cylinders, pistons, piston rings and lubricant for the pistons. Gaskets are made to accommodate a particular engine design and have sealing openings for the cylinders, oil passage opening(s) and water passage opening(s) as well as other apertures or openings, for example, for enabling the gasket to be fixed to the cylinder block (for example using bolts).
Cylinder blocks and cylinder heads are typically cast components and can comprise additional redundant casting legs or bores that are formed during the casting process. These redundant legs are formed as bores or holes and are disposed proximate to the junction between the cylinder head and cylinder block. Whereas these redundant legs could be filled, blocked or otherwise sealed, to do so would incur additional manufacturing cost. If left unblocked, then gas and/or coolant liquid may collect in these redundant casting legs. Openings of the cast legs at the surface of the cylinder block and cylinder head provide a point of egress or ingress for coolant liquid and/or gas out of and into the redundant casting legs. With increasing temperature of the engine, the pressure of the coolant and gas in these redundant casting bores or legs can increase to such a level that uncontrolled leaking may occur. Such leakage may have a detrimental effect on the operation and service life of the engine.
During manufacture the size, shape and location of the redundant casting legs (bores) and their surface openings in the cylinder block and cylinder head are subject to tolerances. The exact size, shape and location of the surface openings of the redundant casting legs is not known until after manufacture. Due to these manufacturing tolerances, an opening of a leg cast in the cylinder head may not be aligned with or superimposed exactly above a corresponding opening of a leg cast in the cylinder block. Indeed, the opening in the cylinder head and the opening in the cylinder block may be off-set from one another and may only partially overlap or indeed not overlap at all.
Typically, known cooling systems for internal combustion engines comprise a pump driven by the engine. Because the cooling system is driven by the engine, the cooling system is operated as soon as the engine is operated. However, for optimum fuel efficiency and to minimise wear on components of an engine, it is better for an engine to operate when it is warm. Operating the cooling system as soon as the engine is initiated, extends the time taken for the engine to warm up and reach an optimum operating temperature. This operation therefore reduces the fuel efficiency of the engine, as well as reducing the service life of the engine. Of particular importance is the temperature of lubricant about the pistons and piston rings. Operation of the engine when the lubricant is below an optimum temperature may have a deleterious effect on the engine.
The invention seeks to provide an improved gasket which addresses or at least mitigates the problems associated with known gaskets. The invention also provides an improved cooling system for an engine that utilises the gasket in combination with a controllable pump. The invention may have advantageous application outside of engines for motor vehicle applications, for example, but not limited to, application in engines for generators.
As used herein the term coolant is used to refer to any suitable temperature management liquid, such as, but not limited to, water, coolant (for example ethylene glycol) and a water and coolant mixture. Upon reading the following description it will be recognised that the terms, “coolant” and “water” are used to refer to liquid and/or fluid that is recirculated to cause cooling of an engine. Additionally, in an advantageous aspect of the disclosure the coolant is maintained at a zero or very low flow-rate to allow warming of an engine to occur. As such the term “coolant” is not intended to be limited to a substance or liquid that causes a reduction in temperature, but rather, and as appropriate, is intended to additionally refer to a liquid or substance that causes or allows for an increase in temperature or maintenance of temperature.